1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device having a fuse portion which is used as, for example, a redundancy relieving circuit or a function adjusting circuit for a mass storage memory, and also to a method of producing the device.
2. Description of the Prior Art
Recently, the fine pattern technique for a semiconductor integrated circuit has been largely advanced. As a result, a memory device configured by a semiconductor integrated circuit, typically, a dynamic random access memory (DRAM) or a static random access memory (SRAM) which has a capacity of a Gbit class has been developed. In order to achieve high integration, wirings for connecting circuit elements are realized by using the multilayer interconnect technology. As the storage capacity of a semiconductor integrated circuit is expanding with the advance of the fine pattern technique, minute dust or the like in the production process causes defective bits which may lower the function of the element or produce a functional failure, whereby the whole of the semiconductor integrated circuit is made defective. This causes a problem in that the production yield is lowered.
As a method of solving the problem, known is a redundancy relief technique. This is a technique of relieving defective bits. In this technique, during a process of producing a chip, spare memory bits are produced in addition to memory bits required in the memory of a product. When there is a defect in a part of the chip and a defective memory bit is therefore produced, the defective memory bit is switched to one of the spare memory bits, so that the whole of the memory bits of a product is configured by non-defective bits. As one of methods of switching a defective memory bit to a spare memory bit, used is a redundancy relief technique based on laser processing in which a fuse portion of a redundancy relieving circuit on a chip is fused and cut off by irradiation with a laser beam, thereby realizing the switching.
In view of simplicity of the production process, conventionally, a material which is mainly composed of polysilicon and silicide that are identical with materials of gate electrodes and bit signal lines of MOS transistors, and polycide configured by laminating polysilicon and silicide is used as a fuse material which is to be laser-processed.
Hereinafter, a fuse portion which is used in a redundancy relieving circuit in the conventional art will be described. FIG. 17 is a section view showing main portions of a conventional semiconductor integrated circuit device. Referring to FIG. 17, 1 denotes a semiconductor substrate, 2 denotes a layer insulating film, 3 denotes fuse portions which are configured by, for example, a polycide layer, 4 denotes an inorganic insulating protective film, 5 denotes an organic insulating protective film, 6 denotes an opening, and 7 denotes a pad electrode which is configured by a metal wiring layer. The pad electrode 7 is an electrode for connecting a lead for package assembling. The organic insulating protective film 5 and the inorganic insulating protective film 4 above the pad electrode 7 are removed away by a usual etching technique so as to form an opening. At the same time, in order to facilitate the cutting of the fuse portions 3 by laser beam irradiation, the organic insulating protective film 5 and the inorganic insulating protective film 4 above the fuse portions 3 are removed away by selective etching to form the opening 6, and a layer insulating film 8 on the fuse portions 3 is thinned.
In a semiconductor integrated circuit device, a multilayer interconnect structure has begun to be employed in order to cope with requirements for high integration and fine patterning. In the configuration of the conventional art, consequently, there arises a new technical problem. Namely, the use of a multilayer interconnect structure causes a large number of wiring layers to exist above a fuse portion which is configured by a polycide layer and the like in the same manner as a gate electrode. As a result, the thickness of the layer insulating film above the fuse portion is increased.
In order to cope with this, by selective etching, an insulating film and a layer insulating film above a fuse portion are removed away and the remaining film is thinned. In order to achieve high integration in a semiconductor integrated circuit device, recently, some multilayer interconnect structures are configured by three or more layers, so that a layer insulating film above a fuse portion has a large thickness. Therefore, the layer insulating film must be etched away by a thickness of about 1 to several pm or more, with the result that the etching removal requires a long time period. This causes the throughput of an etching apparatus to be lowered, thereby producing a technical problem in that the production time period is prolonged. In a large wafer having a diameter of 8 inches or more, furthermore, it is difficult to suppress interfacial unevenness and variation of the etching rate in a etching removal step to a low degree, thereby producing a technical problem in that it is difficult to control correctly and uniformly the thickness of a layer insulating film remaining above a fuse portion, over the whole face of the wafer.
It is an object of the invention to provide a semiconductor integrated circuit device in which a time period required for forming an opening above a fuse portion can be shortened to attain a short production time period, and also a method of producing the device.
The semiconductor integrated circuit device of the invention is characterized in that the device comprises: a layer insulating film formed on a semiconductor substrate; a fuse portion which is configured by an uppermost metal wiring layer that is formed on the layer insulating film; an inorganic insulating protective film which is formed on the metal wiring layer and the layer insulating film; and an organic insulating protective film which is formed on the inorganic insulating protective film, and an opening is formed in the organic insulating protective film so that the inorganic insulating protective on the fuse portion is exposed.
According to this configuration, it is requested only that the fuse portion is formed by the uppermost metal wiring layer formed on the layer insulating film, and the opening is disposed in the organic insulating protective film as an opening above the fuse portion. Unlike the conventional art, it is not required to etch away the layer insulating film in order to form an opening above the fuse portion. Therefore, the time period required for forming the opening can be shortened and the whole production time period can be shortened. Since only the inorganic insulating protective film is formed above the fuse portion, the cutting off of the fuse portion can be performed without excessively increasing the irradiation energy of a laser beam. Therefore, the cutting off of the fuse portion does not cause the reliability to be lowered, nor the production yield to be reduced. Since the fuse portion is covered with the inorganic insulating protective film, the moisture resistance can be improved.
The semiconductor integrated circuit device of the invention may be configured so that the device further comprises an external lead electrode on the layer insulating film, the external lead electrode being configured by the metal wiring layer, and an opening is disposed in the inorganic insulating protective film and the organic insulating protective film which are above the external lead electrode, so as to expose a surface of the external lead electrode.
According to this configuration, the opening above the fuse portion can be formed simultaneously with the opening of the organic insulating protective film and above the external lead electrode, and hence a time period dedicated to forming the opening above the fuse portion is not particularly required.
The semiconductor integrated circuit device of the invention may be configured so that the metal wiring layer is configured by a laminated film having at least a main conducting metal layer and a barrier metal layer which serves as a lower layer, and, in at least a fusion-cut area of the fuse portion, the barrier metal layer of the metal wiring layer configured by the laminated film is removed away.
According to this configuration, the fusion-cut area of the fuse portion is configured by the metal wiring layer in which the lower layer or the barrier metal layer is removed away, and hence the barrier metal layer having a high melting point does not exist in the fuse portion. Consequently, the cutting off of the fuse portion can be performed easily and surely without increasing the irradiation energy of a laser beam, and the lowering of the reliability and the reduction of the production yield which are due to the cutting off of the fuse portion can be further eliminated.
Preferably, the semiconductor integrated circuit device of the invention may be configured so that the metal wiring layer is configured by a laminated film having at least a main conducting metal layer and a barrier metal layer which serves as a lower layer, and, in at least a fusion-cut area of the fuse portion, the barrier metal layer has a thickness of 150 nm or less.
According to this configuration, the fusion-cut area of the fuse portion is configured so that the lower layer or the barrier metal layer is thinned or has a thickness of 150 nm or less. In the process of cutting off the fuse portion by a laser beam, therefore, the cutting off can be surely performed without leaving the barrier metal layer below the fuse portion.
The semiconductor integrated circuit device of the invention may be configured so that the metal wiring layer serving as the fuse portion is embedded into a trench which is formed in the layer insulating film.
Preferably, the semiconductor integrated circuit device of the invention may be configured so that at least one end of the fuse portion configured by the metal wiring layer is connected to a lower wiring layer through a plug electrode in a contact hole which is disposed in the layer insulating film.
According to this configuration, the fuse wiring can be reconnected to the lower wiring layer through the plug electrode in the contact hole, whereby the route along which water and ions permeate from the cut away part of the fuse portion via the fuse wiring which remains after the cutting off is prolonged. Therefore, water and ions are prevented from entering the internal semiconductor element, thereby contributing to improved reliability. In this case, more preferably, a guard band which is configured by a conductive layer may be disposed so as to surround the fuse portion and the contact hole. The inner side of the guard band can block penetration of water and ions, and hence water and ions are prevented from advancing to the outside of the guard band (the semiconductor element portion), thereby contributing to further improved reliability.
Preferably, the semiconductor integrated circuit device of the invention may be configured so that the inorganic insulating protective film on the fuse portion has a thickness which is not smaller than 0.1 xcexcm and not larger than 0.8 xcexcm. According to this configuration, in the process of cutting off the fuse portion by a laser beam, the fuse portion can be easily cut off while preventing the ground of the fuse portion from being damaged.
Preferably, the semiconductor integrated circuit device of the invention may be configured so that a wiring width of the fusion-cut area of the fuse portion is not smaller than 0.1 xcexcm and not larger than 1.0 xcexcm. According to this configuration, in the process of cutting off the fuse portion by a laser beam, the fuse portion can be cut off easily and surely.
The semiconductor integrated circuit device of the invention may be configured so that, with respect to one fuse portion which is electrically continuous, two or more parts are fused off by irradiation with a laser beam. According to this configuration, the electrical cutting off of the fuse portion can be performed more surely.
The semiconductor integrated circuit device of the invention may be configured so that a plurality of fuse portions are disposed in one opening of the organic insulating protective film, and fusion-cut areas of the plurality of fuse portions are arranged on a straight line. According to this configuration, the electrical cutting off of the fuse portions by irradiation with a laser beam can be rapidly performed. Therefore, the throughput is improved so that the productivity can be enhanced.
The method of producing a semiconductor integrated circuit device of the invention characterized in that the method comprises: a first step of forming a fuse portion configured by an uppermost metal wiring layer, on a layer insulating film formed on a semiconductor substrate; a second step of forming an inorganic insulating protective film on the metal wiring layer and the layer insulating film; a third step of forming an organic insulating protective film on the semiconductor substrate on which the inorganic insulating protective film is formed; and a fourth step of forming an opening in the organic insulating protective film so that the inorganic insulating protective on the fuse portion is exposed.
According to this production method, it is requested only that the fuse portion is formed by the uppermost metal wiring layer formed on the layer insulating film, and the opening is disposed in the organic insulating protective film as an opening above the fuse portion. Unlike the conventional art, it is not required to etch away the layer insulating film in order to form an opening on the fuse portion. Therefore, the time period required for forming the opening can be shortened and the whole production time period can be shortened. Since only the inorganic insulating protective film is formed above the fuse portion, the cutting off of the fuse portion can be performed without excessively increasing the irradiation energy of a laser beam. Therefore, the cutting off of the fuse portion does not cause the reliability to be lowered, nor the production yield to be reduced. Since the fuse portion is covered with the inorganic insulating protective film, the moisture resistance can be improved.
Preferably, the method of producing a semiconductor integrated circuit device of the invention may be configured so that the method further comprises the steps of: in the first step, forming an external lead electrode on the layer insulating film, the external lead electrode being configured by the metal wiring layer; after the second step and before the third step, forming an opening in the inorganic insulating protective film above the external lead electrode so as to expose a surface of the external lead electrode; and, in the fourth step, forming an opening in the organic insulating protective film above the external lead electrode so as to expose the surface of the external lead electrode.
According to this production method, since also the external lead electrode is formed by the uppermost metal wiring layer, the opening of the organic insulating protective film above the fuse portion can be formed simultaneously with the opening of the organic insulating protective film above the external lead electrode, and hence a time period dedicated to forming the opening of the organic insulating protective film above the fuse portion is not particularly required.
Preferably, the method of producing a semiconductor integrated circuit device of the invention may be configured so that, in the first step, the metal wiring layer is configured by a laminated film having at least a barrier metal layer and a main conducting metal layer, and the method further comprises the steps of: forming the barrier metal layer on the layer insulating film, the barrier metal layer in at least a fusion-cut area of the fuse portion being removed away; forming the main conducting metal layer on the barrier metal layer and the layer insulating film; and etching the main conducting metal layer and the barrier metal layer into a desired pattern, thereby forming the fuse portion.
According to this production method, the fusion-cut area of the fuse portion is configured by the metal wiring layer in which the lower layer or the barrier metal layer is removed away, and hence the barrier metal layer having a high melting point does not exist in the fuse portion. Consequently, the cutting off of the fuse portion can be performed easily and surely without increasing the irradiation energy of a laser beam, and the lowering of the reliability and the reduction of the production yield which are due to the cutting off of the fuse portion can be further eliminated.
In the method of producing a semiconductor integrated circuit device of the invention, in the first step, a trench may be formed in the layer insulating film formed on the semiconductor substrate, and the metal wiring layer may be then embedded into the trench, thereby forming the fuse portion.
Preferably, the method of producing a semiconductor integrated circuit device of the invention may be configured so that the method further comprises, before the first step, the steps of: forming a wiring trench in a lower layer insulating film which is formed on the semiconductor substrate; forming a lower wiring layer which is embedded into the wiring trench; forming the layer insulating film on the semiconductor substrate on which the lower wiring layer is formed; forming a contact hole in the layer insulating film on the lower wiring layer; and forming a plug electrode in the contact hole, and, in the first step, the fuse portion is formed so that at least one end of the fuse portion is connected to the lower wiring layer through the plug electrode in the contact hole which is disposed in the layer insulating film.
According to this production method, the fuse wiring is connected to the lower wiring layer through the plug electrode in the contact hole, whereby the route along which water and ions permeate from the cut away part of the fuse portion via the fuse wiring which remains after the cutting off is prolonged. Therefore, water and ions are prevented from entering the internal semiconductor element, thereby contributing to improved reliability.
Preferably, the method of producing a semiconductor integrated circuit device of the invention may be configured so that the method further comprises the step of, after the fourth step, etching the inorganic insulating protective film on the fuse portion so as to have a predetermined thickness, the inorganic insulating protective film being exposed in the opening of the organic insulating protective film.
Alternatively, the method of producing a semiconductor integrated circuit device of the invention may be configured so that the method further comprises the step of, after the second step and before the third step, etching the inorganic insulating protective film on the fuse portion so as to have a predetermined thickness. When the inorganic insulating protective film on the fuse portion is etched as described above, the laser cutting of the fuse portion can be easily performed while preventing the ground of the fuse portion from being damaged.
Preferably, the method of producing a semiconductor integrated circuit device of the invention may be configured so that the method further comprises the step of, after the fourth step, with respect to one fuse portion which is electrically continuous, fusing off two or more parts by irradiation with a laser beam. When two or more parts are fused off by laser beam irradiation as described above, the electrical cutting off of the fuse portion can be performed more surely.
Preferably, the method of producing a semiconductor integrated circuit device of the invention may be configured so that a plurality of fuse portions are disposed in one opening of the organic insulating protective film, and fusion-cut areas of the plurality of fuse portions are arranged on a straight line. According to this configuration, the electrical cutting off of the fuse portions by irradiation with a laser beam can be rapidly performed. Therefore, the throughput is improved so that the productivity can be enhanced.